I've been an active skeptic for many years now, and I've been able to find my voice on the internet and IRL. At the JREF, we do a lot of work as well to spread rationality and reason.
I've already written about finding your voice, linking to the really good Rational Moms piece about that. But let's say you're ready to go, and you've got yourself all ready to go. Where can you find out what else is going on, so you can sign up to help?
Have I got the site for you:
is the place to be. It's a compendium of skeptical events for, well, grassroots efforts to make the world a more rational place. They have a calendar with events listed, a forum and links to other venues as well. They're just starting out, so there's not a huge amount of info there yet, but this is a really good idea and could use your support. So go over there, poke around, and send them suggestions on what else they can do.
Make your voice heard!